This invention relates generally to communications and, more particularly, to optical communications systems.
In an optical communications system that utilizes dense wavelength division multiplexing (DWDM), a DWDM signal is created by multiplexing several sequences (or streams) of information bits, e.g., M streams, on M different optical wavelengths (or channels). For example, a DWDM signal may be created by modulating each laser of an M laser array with an associated one of the M information streams and combining the M laser array output signals, where each laser produces light at a different wavelength. Thus, each stream of information is conveyed via a separate optical channel (i.e., by an optical signal having a particular wavelength).
Unfortunately, this mapping of an information stream to a particular wavelength has some drawbacks. For example, if a laser fails the associated information stream is lost. Also, different wavelengths and therefore, different information streams may encounter different levels of impairments (e.g., signal strength degradation and spreading) on the transmission channel between a source node and a destination node. Thus, because of these impairments, one or more signal amplification and/or regeneration stages may be required depending on the distance between the source node and the destination node. This will of course add cost to the system.